IEEE 802.11 describes a communication architecture, which may enable computing devices to communicate via wireless local area networks (WLANs). One of the building blocks for the WLAN is the basic service set (BSS). A BSS may comprise a plurality of computing devices, or stations (STA), which may communicate wirelessly via one or more RF channels within a coverage area. The span of a coverage area may be determined based on the distance over which a source STA may transmit data via an RF channel, which may be received by a destination STA.
An independent BSS (IBSS) refers to a BSS, which comprises a set of STAs, which may communicate with each over within the coverage area for the BSS. In an IBSS each STA may engage in direct communication with any of the other STAs within the IBSS provided that each STA is within the coverage area of the other. An IBSS may be referred to as an ad hoc network.
An infrastructure BSS refers to a BSS, which may be associated with an extended service set (ESS). The ESS is identified by a service set identifier (SSID). An infrastructure BSS may also be referred to as a BSS. Each of the BSSs within an ESS is identified by a BSS identifier (BSSID). Thus, STAs within a BSS generally determine their association within the BSS based on a BSSID and an SSID.
Each BSS comprises a plurality of STAs and an AP. The AP forms an association with each of the STAs within the BSS. The AP identifies each association by an association identifier (AID). The AP may provide communication services to STAs within a BSS based on the presence of an established association.
STAs within a BSS or IBSS may negotiate operating parameters, which the STAs may utilize to enable communications with other STAs within the BSS or IBSS. The operating parameters may include determination of an RF channel bandwidth that is to be utilized between communicating STAs. An RF channel utilized for communication between STAs may utilize a 20 MHz bandwidth or a 40 MHz bandwidth. The operating parameters may also include assignment(s) of RF channels to be utilized by communicating STAs within a given BSS or IBSS. Each RF channel may comprise a distinct range of frequencies as determined by applicable IEEE 802.11 specifications. A 20 MHz RF channel may comprise a single 20 MHz channel. A 40 MHz RF channel may comprise a 20 MHz primary channel and a 20 MHz secondary channel.
The operating parameters may also include specification of a modulation method that is to be utilized by STAs when transmitting data via the assigned RF channel. For example, a STA, for which communications are based on IEEE 802.11g specifications may utilize complementary code keying (CCK) modulation when transmitting data via an RF channel, while a STA, for which communications are based on IEEE 802.11n specifications may utilize orthogonal frequency division multiplexing (OFDM) when transmitting data via an RF channel.
STAs, which utilize IEEE 802.11 specifications may utilize a collision sense multiple access with collision avoidance (CSMA/CA) method to gain access to the wireless medium. Collisions may occur in a wireless communication medium when multiple STAs, within an RF transmission coverage area, concurrently utilize overlapping RF channel(s) in an attempt to transmit data. RF channels may overlap when at least one frequency is common between two or more of the concurrently overlapping RF channels. Collisions may result in unsuccessful transfer of data via the wireless communication medium, which may in turn result in reduced data transfer rates for data transmitted by the STAs. A STA that utilizes CSMA/CA may initiate an attempt to gain access to the wireless medium by transmitting a request to send (RTS) frame. The RTS frame may identify an originating STA, which transmitted the RTS frame, and identify a destination STA, which is the intended recipient of the RTS frame. The RTS frame may be transmitted via the RF channel, which was assigned for communications between the originating STA and the destination STA. When the originating STA and destination STA communicate via a 40 MHz RF channel, the RTS frame may be transmitted via the primary channel.
The RTS frames transmitted by the originating STA may be received by any STA that is within the RF coverage area for RF signals transmitted by the originating STA. The RTS frames sent via the primary channel may be received by STAs within the RF coverage area, which are configured to receive signals transmitted via one or more frequencies within the primary channel bandwidth. The STAs receiving the RTS frame(s) may respond by refraining from attempting to transmit signals via the primary channel for some determined period of time, for example as specified within the RTS frame, thus reducing the likelihood that collisions may occur while the originating STA is transmitting data via the primary channel.
A destination STA may respond to a received RTS frame by sending a clear to send (CTS) frame. The CTS frame may identify that originating STA, which was identified in the received RTS frame by the destination STA. The CTS frame may be transmitted via the RF channel, which was assigned for communications between the originating STA and the destination STA. When the originating STA and destination STA communicate via a 40 MHz RF channel, the CTS frame may be transmitted via the primary channel. Upon receipt of the CTS frame, the originating STA may determine that access to the wireless medium has been acquired.
Once a STA has gained access to the wireless medium, for example subsequent to an RTS/CTS frame exchange, the STA may begin to transmit data via the assigned RF channel while utilizing a specified modulation method. When the originating STA and destination STA communicate via a 40 MHz RF channel, the data may be transmitted via the primary channel and/or secondary channel.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.